package net.neoremind.mycode.argorithm.leetcode;

import net.neoremind.mycode.argorithm.leetcode.support.TreeNode;

/**
 * Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is
 * the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.
 * <p>
 * Example:
 * Given a binary tree
 * 1
 * / \
 * 2   3
 * / \
 * 4   5
 * Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].
 * <p>
 * Note: The length of path between two nodes is represented by the number of edges between them.
 * <p>
 * For every node, length of longest path which pass it = MaxDepth of its left subtree + MaxDepth of its right subtree.
 *
 * @author xu.zhang
 */
public class DiameterOfBinaryTree {

    int max = 0;

    public int diameterOfBinaryTree(TreeNode root) {
        maxDepth(root);
        return max;
    }

    private int maxDepth(TreeNode root) {
        if (root == null) return 0;

        int left = maxDepth(root.left);
        int right = maxDepth(root.right);

        max = Math.max(max, left + right);

        return Math.max(left, right) + 1;
    }

    public int diameterOfBinaryTree2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int dia = depth(root.left) + depth(root.right);
        int ldia = diameterOfBinaryTree(root.left);
        int rdia = diameterOfBinaryTree(root.right);
        return Math.max(dia, Math.max(ldia, rdia));

    }

    public int depth(TreeNode root) {
        if (root == null) {
            return 0;
        }
        return 1 + Math.max(depth(root.left), depth(root.right));
    }
}
